Hydraulically powered steering system for a vehicle having multiple steerable wheels

Abstract

A load transporting vehicle has a plurality of independently steerable wheel sets, each of which incorporates a turntable having a downwardly extending strut and a pivotally mounted trailing arm that carries a pair of wheels. The turntable is rotatably mounted on the vehicle frame. A pair of double acting piston and cylinder assemblies are coupled to rotate the turntable via a rack and pinion. A hydraulic control valve, having a control spool actuated by a boden type cable, controls the flow of hydraulic fluid to the piston and cylinder assemblies. The linear movement of the boden cable is programmed and controlled by rotatable cams. Three or four sets of cams, each set of which controls a different mode of steering, are mounted on a rotatable shaft. Each set of cams has a single cam to a given boden cable and associated wheel set. The sets of cams are interleaved to form groups corresponding to each wheel set. By axially shifting the shaft, a cam follower connected to the boden cable disengages from one cam and engages a next adjacent cam to change from one mode of steering to another. A cam follower lifting mechanism is provided to raise the followers from the cam surfaces during the shifting procedure.

What is claimed is: 
     
       1. In a steering system for a wheeled vehicle including a vehicle frame, a steerable wheel supporting member mounted for rotation about an axis on said frame, a reversible motor means for varying the angular position of said steerable member relative to said frame to steer a wheel supported by said member, a servomechanism operably coupled to said motor means and having a control member for controlling said motor means, an improvement for actuating said control member comprising: a. a first cam and a second cam, each of said cams having a predetermined shape and a rotational axis,   b. coupling means for interconnecting said cams and for mounting said cams for rotation about their respective rotational axes,   c. an operator controlled steering means operably connected to said coupling means for rotating said cams responsive to a command from an operator,   d. follower means for contacting said first cam and for converting the rotational movement of said first cam into linear movement, said follower means being coupled to actuate the control member of said servomechanism to control said motor means, said follower means including i. a first member having a channel therein and first means mounting said first member for reciprocating movement in a radial direction relative to the rotational axes of said cams, said channel being oriented generally parallel to the direction of reciprocation of said first member,   ii. a second member mounted for reciprocating movement in the channel of said first member,   iii. a cam follower having an end thereof contacting the cam surface of one of said cams, said cam follower being connected to said second member,   iv. second means biasing said follower means toward said cam surface, and   v. third means for biasing said second member toward said cam surface relative to the position of said first member, and     means for relatively axially shifting said first and second cams and said follower means so that said follower means is shifted relative to said first cam and is positioned to contact said second cam and to convert rotational movement of said second cam into linear movement to actuate said control member and control said motor means.   
     
     
       2. The improvement of claim 1 wherein said third means has a greater biasing force than said second means. 
     
     
       3. The improvement of claim 2 wherein said third biasing means comprises a spring mounted in compression in the channel in said first member. 
     
     
       4. The improvement of claim 2 wherein said second means comprises: first and second arms affixed to and extending transversely outwardly in mutually opposing directions from said second member,   a first extensible spring coupled to said first arm and a second extensible spring coupled to said second arm, said first and second springs being operably fixed relative to said coupling means to bias said follower means toward said cam surface.   
     
     
       5. In a steering system for a wheeled vehicle including: a vehicle frame,   a plurality of steerable wheel supporting members mounted for rotation about mutually parallel axes on said frame, each of said wheel supporting members having a reversible motor means for varying the angular position of said steerable member relative to said frame to steer the wheel supported by said member, and a servomechanism operably coupled to said motor means and having a control member for controlling said motor means, and   an operator controlled steering means,   the improvement for translating the motion of said operator controlled steering means to actuate the control member of said servomechanism comprising: a. a housing,   b. a shaft mounted in said housing for rotation about its rotational axis and for axial movement relative to its rotational axis,   c. a plurality of axially spaced cam groups fixed to said shaft, each of said cam groups having at least a first and second cam corresponding to first and second cams in the remainder of said cam groups, each of said first and second cams having a cam surface, said first cams forming a first set for steering said vehicle in a predetermined steering mode, said second cams forming a second set for steering said vehicle in a second predetermined mode,   d. a plurality of follower means mounted in said housing for reciprocating movement in a radial direction relative to said cams, each follower means being associated with and corresponding to one of said cam groups, said follower means for simultaneously contacting one of said sets of cams,   e. a plurality of cables and a sheath housing each of said plurality of cables for reciprocating movement therein, one end of each of said cables being associated with and connected to a corresponding one of said follower means, the corresponding end of each sheath being affixed to said housing, the other end of said cable being affixed to a corresponding control member of a corresponding one of said plurality of wheel supporting members,   f. means for translating the motion of said operator controlled steering means to rotary motion in said shaft,   g. means for axially shifting said shaft relative to said plurality of follower means so that said plurality of follower means is disengaged from one of said sets of cams and is engaged with another of said sets of cams, and   h. means for lifting said follower means away from said cam surfaces as said cams and said follower means are being relatively axially shifted including i. a first arm oriented transversely relative to the direction of reciprocation of said follower means and mounted to reciprocate in a direction generally parallel to the direction of reciprocation of said follower means, said first arm being oriented so as to be moveable between a first position and a second position displaced away from said cam relative to said first position, and   ii. a second arm coupled to said follower means, said first arm in said first position being disengaged from said second arm, said first arm in said second position engaging said second arm and causing said second arm to move said follower means radially away from said cam surface.       
     
     
       6. The system of claim 5 further comprising: i. a shaft extension coupled coaxially to said shaft, said shaft extension being coupled to axially shift said shaft relative to said follower means, said shaft being coupled to said shaft extension for rotation relative thereto,   j. an arm pivotally attached to said shaft extension, said arm being oriented transversely relative to the rotational axis of said shaft, for pivotal movement about a pivotal axis oriented generally transversely relative to the rotational axis of said shaft,   k. first linearly acting power means having a drive member moveable between at least a first and second position in a direction generally parallel to the rotational axis of said shaft, and   l. a second linearly acting power means having a member moveable between at least a first and second position in a direction generally parallel to the rotational axis of said shaft, the moveable member of said first power means being pivotally attached to one end of said arm, the moveable member of said second power means being pivotally attached to the opposite end of said arm, the pivotal attachments of said moveable members to said arm being located on mutually opposite sides of the location of the pivotal attachment of said arm to said shaft extension, said arm being located in a first position wherein said follower means reside over and contact said first set of cams when said first and second power means are positioned respectively in their first and first positions, said arm being shifted to a second position wherein said shaft is axially moved so that said follower means reside over and contact said second set of cams when said first and second power means are respectively in their first and second positions, and said arm being shifted to a third position wherein said shaft is axially moved so that said follower means reside over and contact said third set of cams when said power means are respectively in their second and second positions.   
     
     
       7. In a steering system for a wheeled vehicle including a vehicle frame, a steerable wheel supporting member mounted for rotation about an axis on said frame, a reversible motor means for varying the angular position of said steerable member relative to said frame to steer a wheel supported by said member, a servomechanism operably coupled to said motor means and having a control member for controlling said motor means, an improvement for actuating said control member comprising: a first cam, a second cam and a third cam, each of said cams having a predetermined shape and a rotational axis,   a coupling shaft mounted for rotation relative to a frame and interconnecting said cams for rotation about their respective rotational axes,   an operator controlled steering means operably connected to said coupling means for rotating said cams responsive to a command from an operator,   follower means for contacting said first cam and for converting the rotational movement of said first cam into linear movement, said follower means being coupled to actuate the control member of said servomechanism to control said motor means, and   means for relatively axially shifting said first, second and third cams and said follower means so that said follower means is shifted relative to said first cam to contact one of said second and third cams and to convert the rotational movement of said one of said second and third cams into linear movement to actuate said control member and to control said motor means, said means for shifting including an arm and mounting means mounting said arm to said shaft for rotation relative to said shaft and for pivotally attaching said arm to said shaft for rotation about an axis oriented generally transversely relative to the rotational axes of said cams, said arm being oriented generally transversely relative to the rotational axes of said cams,   first linearly acting power means having a member moveable between at least a first and a second position, and   a second linearly acting power means having a member moveable between at least a first and second position, the moveable member of said first power means being pivotally attached to one end of said arm, the moveable member of said second power means being pivotally attached to the opposite end of said arm, the pivotal attachments of said moveable members to said arm being on mutually opposite sides of the location of the pivotal attachment of said arm to said shaft, said arm being located in a first position wherein said follower means resides over the surface of said first cam when said first and second power means are positioned respectively in their first and first positions, said arm being shifted to a second position wherein said shaft is axially moved so that said follower means resides over said second cam when said first and second power means are respectively in their first and second positions, said arm being shifted to a third position wherein said shaft is axially moved so that said follower means resides over said third cam when said first and second power means are respectively in their second and second positions.   
     
     
       8. In a steering system for a wheeled vehicle including a vehicle frame, a plurality of steerable wheel supporting members mounted for rotation about mutually parallel axes on said frame, each of said wheel supporting members having a reversible motor means for varying the angular position of a respective steerable member relative to said frame to steer the wheel supported by said member, and having a servomechanism operably coupled to said motor means, said servomechanism having a control member for controlling said motor means, an improvement for actuating the control member associated with each of said wheel supporting members comprising: a plurality of axially spaced cam groups and coupling means for interconnecting and mounting said cams for rotation about their respective rotational axes, each of said cam groups having at least a first and second cam corresponding to first and second cams in the remainder of said cam groups, each of said first and second cams having a cam surface, said first cams forming a first set for steering said vehicle in a first predetermined steering mode, said second cams forming a second set for steering said vehicle in a second predetermined steering mode,   an operator controlled steering means operably connected to said coupling means for rotating said cams responsive to a command from an operator,   a plurality of follower means simultaneously contacting one of said sets of cams, each of said follower means being associated with and corresponding to one of said cam groups, each of said follower means being operably associated with a respective servomechanism on each of said plurality of wheel supporting members to actuate a respective control member to control a respective motor means,   means associated with said cams for mounting said follower means for reciprocating movement in a generally radial direction relative to the rotational axes of said cams,   means for relatively axially shifting said cams and said plurality of follower means so that said plurality of follower means is shifted relative to the first cam in each of said cam groups and positioned to contact a second cam in each of said cam groups and to convert the rotational movement of said second cam in each of said cam groups into linear movement to actuate a respective control member to control a respective motor means, and   means for simultaneously moving said plurality of follower means away from said cams in a generally radial direction relative to the rotational axes of said cams when said cams and said plurality of follower means are being relatively axially shifted.   
     
     
       9. In a steering system for a wheeled vehicle including a vehicle frame, a steerable wheel supporting member mounted for rotation about an axis on said frame, a reversible motor means for varying the angular position of said steerable member relative to said frame to steer a wheel supported by said member, a servomechanism operably coupled to said motor means and having a control member for controlling said motor means, an improvement for actuating said control member comprising: a. a first cam and a second cam, each of said cams having a predetermined shape and a rotational axis,   b. coupling means for interconnecting said cams and for mounting said cams for rotation about their respective rotational axes,   c. an operator controlled steering means operably connected to said coupling means for rotating said cams responsive to a command from an operator,   d. follower means for contacting said first cam and for converting the rotational movement of said first cam into linear movement, said follower means being coupled to actuate the control member of said servomechanism to control said motor means, said follower means being mounted to reciprocate in a generally radial direction relative to the axes of rotation of said cams,   e. means for relatively axially shifting said first and second cams and said follower means so that said follower means is shifted relative to said first cam and is positioned to contact said second cam and to convert rotational movement of said second cam into linear movement to actuate said control member and control said motor means, and   f. means for lifting said follower means away from said cam surface as said cams and said follower means are being relatively axially shifted, said means for lifting including i. a first arm oriented transversely relative to the direction of reciprocation of said follower means and mounted to reciprocate in a direction generally parallel to the direction of reciprocation of said follower means, said first arm being oriented so as to be moveable between a first position and a second position displaced from said cam relative to said first position, and   ii. a second arm coupled to said follower means, said first arm in said first position being disengaged from said second arm, said first arm in said second position engaging said second arm and causing said second arm to move radially away from said cam surface, thereby causing said follower means to lift away and disengage from said cam surface.     
     
     
       10. In a steering system for a wheeled vehicle including: a vehicle frame,   a plurality of steerable wheel supporting members mounted for rotation about mutually parallel axes on said frame, each of said wheel supporting members having a reversible motor means for varying the angular position of said steerable member relative to said frame to steer the wheel supported by said member, and a servomechanism operably coupled to said motor means and having a control member for controlling said motor means, and   an operator controlled steering means,   the improvement for translating the motion of said operator controlled steering means to actuate the control member of said servomechanism comprising:   a housing,   a shaft mounted in said housing for rotation about its rotational axis and for axial movement relative to its rotational axis,   a plurality of axially spaced cam groups fixed to said shaft, each of said cam groups having at least a first and second cam corresponding to first and second cams in the remainder of said cam groups, each of said first and second cams having a cam surface, said first cams forming a first set for steering said vehicle in a predetermined steering mode, said second cams forming a second set for steering said vehicle in a second predetermined mode,   a plurality of follower means mounted in said housing for reciprocating movement in a radial direction relative to said cams, each follower means being associated with and corresponding to one of said cam groups, said follower means simultaneously contacting one of said sets of cams,   a plurality of cables and a sheath for each of said plurality of cables, one end of each of said cables being associated with and connected to a corresponding one of said follower means, the corresponding end of each sheath being affixed to said housing, the other end of said cable being affixed to a corresponding control member of a corresponding one of said plurality of wheel supporting members,   means for translating the motion of said operator controlled steering means to rotary motion in said shaft,   means for axially shifting said shaft relative to said plurality of follower means so that said plurality of follower means is disengaged from one of said sets of cams and is engaged to contact another of said sets of cams, and   means for simultaneously lifting said plurality of follower means away from said cam surfaces in a radial direction relative to said cams as said shaft is axially shifted relative to said cams.